Thousands of antibodies are produced every year by commercial companies. However, many of these antibodies are known to be poorly characterized and suboptimal across multiple applications. Polyclonal antibodies lack the reproducibility of monoclonal antibodies. Likewise, the production of monoclonal antibodies is expensive and may take months to produce. Even after production, a monoclonal antibody may not be specific for the target of interest, may not work in the needed assay, or could not be used in the needed assay, or could not be used in combination with other antibodies due to an antibody's large size and subsequent competition for overlapping binding domains. As such, the high costs associated with producing even small quantities of monoclonal antibodies represent a large barrier towards cost-effective reagents and resources for proteomic technology research and clinical adaptation. This project utilizes a new tool, "massively parallel selection of DNA aptamers" to rapidly identify high-affinity ligands to hundreds or even thousands of protein targets simultaneously. In this Phase I project, we will demonstrate the utility of our tool for selecting aptamers to 100 important cancer biomarkers and characterize many of them by accepted practices. The developed reagents will have tremendous value to the research community and potential to alleviate human suffering due to cancer.